摘要：In order to achieve high precision measurement of inductance in a wide frequency range,a method of inductance measurement based on double-excitation auto-balancing bridge is *** this method,the direct digital synthesizer(DDS)as signal generator is used as the bridge excitation source,and the bridge is automatically balanced by adjusting and measuring the voltage *** standard resistors,the system can achieve high precision measurement of four-terminal pair inductors in the frequency range of *** at the low efficiency of bridge balancing,an iterative balancing algorithm based on the steepest descent method is *** order to suppress the interference caused by the initial phase change and non-integer periodic sampling,the high-precision measurement of the complex impedance of inductance is realized based on the all-phase fast Fourier transform(apFFT).Finally,the corresponding measurement system is built and the inductance measurement experiment is carried *** experimental results show that the relative error of the system for inductance measurement can be as low as 0.009%,and the optimal relative measurement uncertainty of the system can reach 9.89×10^(-4)compared with 5×10^(-5)of commercial impedance analyzer.

摘要：智能合约的发展处于初期阶段,底层编程语言和应用平台的不同使得智能合约的设计缺少规范,极易出现漏洞,造成损失。针对以太坊区块链平台上智能合约存在的安全漏洞问题,提出了一种基于模糊测试的智能合约正确性检测方法。该方法根据智能合约内容及规范生成模糊输入,并根据模糊输入在以太坊虚拟机内执行智能合约,监控合约在执行过程中的行为,生成多个日志文件,提取日志文件中的关键信息,对测试用例进行触发测试,从而得到智能合约所包含漏洞的情况,实现正确性检测。在实验过程中,该方法针对416个智能合约中的七类常见漏洞进行了漏洞检测,标记出了19个存在漏洞的智能合约。经过人工审计分析发现,在这19个被标记的不正确智能合约中,有18个智能合约确实存在安全漏洞。实验结果表明所提方法能够以较高的准确率识别智能合约中包含的漏洞,从而检测智能合约的正确性。

摘要：The disguised covert detection method that imitates whale calls has received great attention in recent years because it can solve the traditional problem of the trade-off between long-range detection and covert ***,under strong reverberation conditions,traditional echo signal processing methods based on matched filtering will be greatly *** on this,a disguised sonar signal waveform design is proposed based on imitating whale calls and computationally efficient anti-reverberation echo signal processing ***,this article proposed a disguised sonar signal waveform design method based on imitating whale *** method uses linear frequency modulation(LFM)signals to replace LFM-like segments in real whale calls,and extracts the envelope of the real whale call’s LFM-like segment to modify the LFM ***,this article proposed an echo signal processing method of fractional Fourier transform(FrFT)based on target echo locating of synchronization *** method uses the synchronization signal to locate the target echo,and determines the step-size interval of the FrFT based on the information carried by the synchronization *** with the traditional FrFT,this method effectively reduces the amount of calculation and also improves the anti-reverberation ***,the excellent performance of the proposed method is verified by simulation results.

摘要：随着中国标准化引领供给侧结构性改革持续推进,粮食行业发展迈入新阶段,政府主导与市场驱动相互协调的二元新型标准体系基本建立,粮食行业标准体系覆盖粮油收购、储存、加工、运输、销售的全链条,顶层设计精简国家标准、优化行业标准、彰显地方标准、培优团体标准、搞活企业标准。但粮食行业标准体系出现一些新问题,如标准结构不合理,原始创新动力不足等。面对产业发展新需求,统筹规划粮食标准体系框架、聚焦节粮减损绿色生态领域等手段是增加标准有效供给和保障能力,打造体系健全、技术创新、先进合理、开放融合的格局,引领粮食行业高质量发展,实现粮食行业现代化的重要抓手。

摘要：Three drums with different helical angles （15°, 20°, and 25°） were developed to investigate improved loading performance of the shearer drum. Nine trials were performed at different drum rotation speeds （80, 100, and 120 r/min） and different haulage speeds （1.5, 2.0, and 2.5 m/min） in an orthogonal test design. Loaded coal quantity and cutting power of the drum were the responses measured under the dif- ferent conditions. The effect of the parameters was determined by means of the extreme difference method. The significance of the effects was determined by analysis of variance. The results indicate that the effect from changes in the helical vane on loading performance of the drum is the largest in magnitude. The haulage speed has the least affect on loading performance. The helical angle has the least affect on cutting power of the drum. Haulage speed has the largest affect on the cutting power of the drum. 2011 Published by Elsevier B.V. on behalf of China University of Mining ＆ Technology.

摘要：叶尖间隙是航空发动机设计和试验的关键参数,直接影响发动机的工作效率和运行安全。航空发动机叶尖间隙的实时在线监测已成为测试大纲中的必备项目。随着新型航空发动机的发展,叶尖间隙测量技术进一步成熟和深入。介绍了叶尖间隙在线测量原理,阐述了系统典型结构及常用测量流程,归纳了叶尖间隙在线测量的6大关键技术,详细分析了放电探针法、光纤法、电容法、电涡流法和微波法等叶尖间隙测量方法的工作原理、性能特征、关键技术发展历程及未来发展方向,对比总结了各种方法的研究成果和最新产品,提出了叶尖间隙测量领域的发展趋势与展望,从6个方面总结了叶尖间隙测量领域的未来重点研究方向,为后续研究提供参考。

摘要：针对现有倾角传感器分辨力不足、精度不高、线性度差等问题,设计了一种使用柔性铰链连接极板和外框架进行角度传递的差动电容式倾角传感器,该传感器兼具稳定性好、分辨力高和线性度好的优点。提出了在检测能力一定的情况下通过改变结构参数获得不同分辨力和量程的倾角传感器设计方法。分析了差动式电容极板测倾角原理并进行了线性度评定。构建了结构参数对传递灵敏系数的影响模型,根据选择的结构参数设计了传感器并结合数字电容检测电路进行了验证。实验结果表明在±1000″量程范围内分辨力优于0.14″,测量误差小于±2″,线性度优于0.17%。

摘要：目前,区块链由于其高度的去中心化以及不可篡改的特性被广泛应用于不同领域,文章以解决区块链在应用过程中的链间数据交互一致性无法保证以及不支持数据动态更新的问题为研究目标,设计了一种去中心化的数据一致性审计模型,该模型采用跨链技术来实现异构区块链之间数据的安全可信共享,利用去中心化的变色龙哈希函数构建动态的默克尔哈希树以实现数据的动态更新操作,引入审计链对源链和目标链之间的数据交互进行监管,并利用Cosi多重签名算法来保证数据传输过程中的一致性。经过理论分析和实验验证,结果表明,该模型采用的Cosi算法在时间开销和可扩展性方面与目前主流多重签名算法相比具有较大优势。此外,本文模型在时间开销和通信开销方面与常见的审计模型相比有较大优势,能够以较小的成本完成相同的审计任务,并且可以达到99%的数据审计一致性保证概率。

摘要：设计了一种基于AT89C55单片机的智能火灾两级报警与联动控制系统。此系统结合多种火灾因素探测器和运用模糊神经网络算法来提高报警的可靠性,采用两级报警和主控中心联动灭火的设计提高报警和自动灭火的及时性。分别说明了系统的硬件电路设计、系统的通讯方式和软件设计思想。这一设计可提高火灾报警系统的可靠性与及时性,减少误报率,提高系统的智能化程度。

摘要：中继链是被广泛认可的跨链技术之一,当前跨链多采用实用拜占庭容错及其改进算法,如加权拜占庭容错(Weighted Practical Byzantine Fault Tolerance,WPBFT)算法。WPBFT算法为节点附加权重,降低恶意节点的影响,但其权重更新机制简单,作恶成本较低,严重威胁了系统的安全。为此,针对中继链安全和效率需求,文章提出一种应用于中继链的改进加权拜占庭容错(Improved Weighted Practical Byzantine Fault Tolerance,IWPBFT)算法。该算法对WPBFT算法的共识过程和权重变更机制进行改进,设计了新的权重更新和节点奖惩机制。实验表明,IWPBFT算法主节点出错概率较低,共识成功率较高,可有效提高中继链的安全性、可靠性和容错性,降低共识时延,提升中继链的跨链效率。